The present invention relates generally to metal alkoxide compounds and more particularly to a tridentate-ligated tin alkoxides and their method of preparation.
Tin alkoxides are used in applications ranging from electro-active ceramics, conductors, semiconductors, and catalysts. Even though the shape and type of metal cation structures used for metal alkoxide architecture can be well controlled at the atomic-level, metal alkoxides have not been generally used as catalysts. Typically, those metal alkoxides that are used as catalysts involve alkali metal alkoxides. Alkyl aluminum alkoxides have also been used as part of a complex mixture to oligomerize ethylene (U.S. Pat. No. 4,686,315, issued on Aug. 11, 1987). There are also some reports of Group IV metal alkoxide for the production of polyacrylates, polyamides, and allylic alcohols (U.S. Pat. No. 4,496,776, issued on Jan. 29, 1985; U.S. Pat. No. 4,549,017, issued on Oct. 22, 1985). However, in general these materials are used as supports and not necessarily the active site of polymerization.
Sommer et al. (U.S. Pat. No. 4,675,411, issued on Jun. 23, 1987) and McEntire et al. (U.S. Pat. No. 4,613,673, issued on Sep. 23, 1986) using tin alkoxides have been reported; however, these compounds are reacted to form in situ compounds that are not metal alkoxides but metal amides.
The low use of metal alkoxides as catalysts is typically attributed to the large charge/cation size ratio that leads to cluster formation to satisfy the various cation's coordination sphere demands. Because of this hyper-oligomerization, reactive sites on the metal are rendered inaccessible. Even for those metal alkoxides that do not oligomerize, ligand rearrangement results in solution functionality that again can neutralize potential active sites. Thus, metal alkoxides are typically poor catalysts due to hindered reactive sites. This is typically due to the dynamic behavior metal alkoxide compounds exhibit in solution coupled with the large cation to small charge ratio that promotes oligomerization.
Useful would be tin compounds that have available electrons that can be used both in solution and as thin films.